In this application, studies are proposed to further define the cis- acting sequences and trans-acting factors involved in the cell-specific, developmental and multifactorial regulation of expression of the rabbit SP-A gene. We will introduce SP-A:hGH fusion genes containing various deletions or mutations in the potential SP-A gene regulatory elements into transgenic mice and transfected type II cells in culture to define the cis-acting elements required for type II cell-specific, developmental and multifactorial regulation of expression. The genomic elements found to mediate lung-specific and appropriate developmental regulation of expression will be used to isolate cDNA inserts encoding lung-specific transcription factors (LTFs) which will be characterized and analyzed for their ability to mediate SP-A gene expression. LTF cDNA and cRNA probes will be used in studies to analyze the cell-specific, developmental and hormonal regulation of LTF gene expression. LTF cDNAs will be used to isolate the LTF gene(s); targeted mutations introduced into the LTF gene(s) in transgenic mice will provide information regarding their role in the regulation of surfactant protein gene expression and in lung morphogenesis. In consideration of the major role played by cAMP in the regulation of SP-A gene expression, studies will be implemented to define the mechanisms whereby cAMP regulates SP-A gene expression in developing lung. It is hoped that our studies to define the basic mechanisms involved in the developmental and cell-specific regulation of surfactant protein gene expression will ultimately lead to the design of therapies that will reduce the incidence and consequences of RDS in prematurely born infants.